An air conditioner

ABSTRACT

An air-conditioner having a compressor, and a condenser. The air conditioner has a desuperheater provided in a flow path from the compressor to the condenser.

TECHNICAL FIELD

The present disclosure relates to an air-conditioner. In particular thepresent disclosure relates to a portable air-conditioner.

BACKGROUND

Air conditioning (AC) is a collective expression for conditioning airinto a desired state. It could be heating the air during cold periods,cooling the air during warmer periods or for cleaning the air if itcontains unwanted particles. However, the expression air conditioning ismost often used when emphasizing cooling. As a product, air conditionerscan look and be used in various ways, but they all share the same basictechnology.

Existing portable air-conditioners are often found to be large, hard tohandle, noisy and inefficient. Furthermore, the connected exhaust airoutlet that removes the heat from the room is often complicated andinefficient in its design. A known portable air-conditioner is forexample described in the U.S. Pat. No. 2,234,753.

The design of portable AC systems differs from other Air Conditionersbecause all the components of the system are mounted inside of a packedunit which has to work inside of the conditioned space, releasing theresidual energy (generated in the normal cooling process) through an airexhaust system which is usually connected to the outside.

In portable AC units there are two general procedures to cool down anair source condenser: single duct and dual duct methods. In the firstone (single duct), the system takes air from its surroundings(conditioned space), forcing it to pass through the condenser surfaceand eventually removing the residual energy from it. Then, the hot airis expelled outdoors by using a single duct system. In this method, theintake air temperature has the indoor temperature conditions, whichmakes the energy exchange process more beneficial from standpoint of therefrigerant cycle.

In the dual duct method, the system uses an air intake duct to inject“hot” air from outdoor to cool down the condenser. Eventually the aircoming from condenser at a relatively high temperature is releasedoutdoors again by a secondary exhaust duct. In this method the airintake temperature is at the outdoor temperature conditions. This methodcan provide a quicker cooling effect for the user, since the system isnot using the indoor air as a coolant media for condenser, but requiringin turn a larger size/volume of components to compensate the higherinlet outdoor temperatures.

Both methods, single and dual duct, have different limitations in termsof: air flow rates, size of the heat exchangers and also dimensions ofthe air piping system.

Those particularities requires that the portable AC systems make use ofparticular size of condensers, limiting the maximum air flow rate usedby the system, since the air intake and air exhaust systems have to beas much compact as possible.

Air flow rates in portable AC systems are also limited by the noiselevels, since larger air flow rates flowing through small diameter hoseslead to higher pressure drops and higher noise levels. In that sense,the single duct systems have a clear advantage over the dual ductsystems, because the temperature difference between the intake air andthe condensing temperature of the cycle is larger, requiring lower airflow rates to perform the heat rejection process.

So, for portable AC systems, the condenser is one of the most criticalcomponents to design, since it has to exchange higher heat loads with avery limited air flow rate. Therefore, that particularity affects in asignificant way the whole design of the condenser and the whole systemperformance.

One way to improve the condenser capacity in portable AC systems is bythe use of the condensed water coming from the evaporator, at arelatively low temperature, in order to remove part of the heat load ofthe condenser.

Some portable AC designs are provided with a drainage system that usesthe water coming from evaporator which is dripped over the condenser,allowing a decrease of the surface temperature and subsequently gettinglower condensing pressures in the cycle.

In addition to the dripping method, some other systems include the useof a wheel that splashes the excess of non-evaporated water from thebottom of condenser over its surface. This mechanism allows theelimination of part of the excess of water through the air stream thatcrosses the condenser.

Such methods help to decrease the condensing temperatures in the coolingcycle and also to remove part of the undesired condensed water generatedin the normal operation process of the system.

There is a constant desire to improve the operation of air-conditioners.

Hence, there is a need for an improved air-conditioner.

SUMMARY

It is an object of the present invention to provide an improvedair-conditioner that at least partly solves problems with existingair-conditioners. In accordance with one aspect problems related to thetechnology of the vapor compression cycles for air conditioners aretargeted, in particular those related with portable AC units workingwith air source heat exchangers.

This object and others are obtained by the portable air conditioner asset out in the appended claims. Also disclosed are devices that can beused together with portable air-conditioners.

By the use of an external desuperheater which has the function to startthe condensation of refrigerant before it enters into the condenser,normally an air cooled heat exchanger, it is possible to take advantageof a larger temperature difference between the hot gas delivered by thecompressor and the cold water dripped from the evaporator surface.

In accordance with one embodiment an air-conditioner is provided. Theair-conditioner has a compressor and a condenser. The air conditionerfurther has a desuperheater provided in a flow path from the compressorto the condenser.

In accordance with some embodiments the air-conditioner is a portableair-conditioner.

In accordance with some embodiments the desuperheater is located in anopen cavity.

In accordance with some embodiments the air-conditioner is adapted tofeed condensation water to the open cavity.

In accordance with some embodiments a pipe is provided and adapted tolead condensed water that drops from the evaporator to the open cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in more detail by way ofnon-limiting examples and with reference to the accompanying drawings,in which:

FIG. 1 illustrates a T-S diagram for a standard refrigeration cyclewhich uses an air source heat exchanger as condenser,

FIG. 2 illustrates a T-S diagram for a refrigeration cycle, which usesan external desuperheater,

FIG. 3 depicts an air-conditioner with an external desuperheater,

FIGS. 4 and 5 depicts different shapes of a portable air-conditioner ina side sectional view and a top sectional view respectively,

FIG. 6 shows a possible configuration of an embodiment with a coatingmaterial over connection pipes.

FIG. 7 show possible embodiments of coating elements over the connectionpipes.

FIG. 8 shows an embodiment including an auxiliary water pumping systemto remove non-condensed water,

FIG. 9 shows an embodiment with non-evaporated water collected in awater tank, and

FIG. 10 illustrates the general principles of an air conditioner system.

DETAILED DESCRIPTION

In standard portable ACs, working with air source heat exchangers, theheat rejection process starts when the hot gas delivered by thecompressor enters into the condenser. Inside of condenser, therefrigerant at high pressure and temperature starts its cooling downprocess releasing its heat load through the air stream that crosses theheat exchanger surface.

At those conditions, a significant percentage of the total area of thecondenser is intended first to decrease the bulk temperature of the gasuntil it reaches the saturation temperature in an internalde-superheating process. As the density of the superheated vapour flowis relatively low, the volume occupied by the refrigerant is relativelylarge, especially before to start the phase-change process ofcondensation.

This fact makes that the size of the heat exchanger, especially the areaand internal volume intended to de-superheating the refrigerant, tend tobe larger to contain the hot gas in order to decrease its bulktemperature until it reaches the saturation conditions. Then, once thethermodynamic vapour quality of the refrigerant is equal to 1, thecondensation and the subsequent subcooling processes will take place inthe remainder heat exchanger internal volume.

FIG. 10 illustrates the general principles of an air conditioner system.The main parts of the system are the compressor 101, evaporator 103,condenser 105, and expansion device 107 such as a capillary tube. Also acondenser fan 109 and an evaporator fan 111 can be provided. Thecompressor is connected in a circuit with the condenser, the evaporator,and the expansion device. The refrigerant has the ability to turn fromliquid into vapor, and by that change in temperature. The temperedrefrigerant and the indoor air work in symbiosis to exchange heat toeach other.

FIG. 1 shows a T-S diagram for a standard refrigeration cycle which usesan air source heat exchanger as condenser, which works under typicaltemperature conditions for a portable AC application. FIG. 1 includes aline that represents the inlet and outlet temperatures of the air flowrate that crosses the condenser (blue line), and the standard approachesfor the heat rejection sub-processes that take place inside ofcondenser: DSH, Phase-Change, Subcooling.

In the heat rejection process shown in FIG. 1, the superheated vapourrejects first sensible heat along the single-phase desuperheating zone(DSH). Then, condensation starts from the equilibrium vapour quality 1,where saturated refrigerant rejects latent heat during its condensation(2-phase process). Finally, in the last part of the condenser, thesubcooled liquid rejects sensible heat through the single-phasesubcooling zone (SC). Desuperheating can be described as the process bywhich a superheated steam is restored to its saturated state, or thesuperheat temperature is reduced. This process can be performed by adesuperheater.

In air cooled condensers, the temperature of the air stream around thedesuperheating section affects strongly the gas desuperheating process.Air surrounding temperature is usually affected by the circuiting designand other geometrical parameters like the relative location of therefrigerant inlet ports, the number of passes, the number of rows, airflow rates, etc.

However, in the particular case of portable AC systems, the geometricallimitations in the dimensions of the air exhaust ducts restrict the airflow across the condenser, leading to achieve larger temperaturegradients through the air path that crosses the condenser from inlet tooutlet, therefore the air temperature around the desuperheating sectiontend to be much higher.

On the other hand, as the fluids flow arrangement is generally fixed ina counter-current flow type configuration, in most of the cases thedesuperheating section of condenser rejects energy against an air flowthat has previously exchanged energy with the first rows of condenser.This fact affects also to the increase of the air stream temperaturethat surrounds the back rows of condenser, where usually are located thedesuperheater inlet ports.

Both effects, the higher temperature gradients of the air surroundingthe desuperheating zone of condenser and the relative position of theinlet gas ports make that the wall temperatures of the pipes in thedesuperheater area are normally higher than the saturation temperatureof the refrigerant, leading a long an inefficient desuperheating processinside of condenser and subsequently requiring larger heat transferareas to complete the condensation process.

In order to improve the heat transfer processes in air sourcecondensers, in particular air cooled condensers used in portable airconditioners an external desuperheater can be provided.

The desuperheater enables the heat transfer between the discharge gasdelivered by the compressor, at high pressure and temperature, and thecondensed water generated on the evaporator surface at a relatively lowtemperature.

In a standard condensation process, without the use of an externaldesuperheater, part of the energy exchange area is intended to decreasethe temperature of the superheated gas until it reaches the saturationconditions. The area used to perform this process can be between 10 to20% of the total heat transfer area of condenser. The heat load removedat those conditions is usually relatively small because of the low heattransfer coefficients achieved in the single phase exchange process,especially using air as secondary coolant media.

The use of an external desuperheater described herein takes advantage ofthe higher heat transfer coefficients achieved by a faster condensationof the refrigerant, because of the large temperature difference betweenfluids, but also because of the improvement in the heat transfercoefficients of the secondary coolant media (water), due to its partialevaporation (2-phase process).

FIG. 2 represents the T-S diagram for an improved cycle compared to FIG.1, which uses an external desuperheater. The external desuperheater canbe installed just before the air cooled condenser.

FIG. 2 represents the three different heat rejection sub-processes:desuperheating of vapour using condensed water, saturated condensationand subcooling, by the standard heat rejection against an air stream. InFIG. 2 are also represented the temperature profiles of secondarycoolant media: condensed water in the case of desuperheating and air inthe case of condensation and subcooling.

The desuperheating is carried out by the external desuperheater, wherethe film condensation of the vapour appears almost instantaneously overthe internal surface of the heat exchanger because under thoseconditions, the wall temperature of the desuperheater is far below ofthe saturation temperature of the refrigerant, since the heat exchangeris surrounded by the condensed water at relatively low temperatureconditions.

As the temperature of the water coming from evaporator is generally thedew point temperature of the air that leaves the evaporator, the heatrejection process inside of the desuperheater is then driven by: thesensible heat rejection due the vapour desuperheating, and the latentheat rejection to generate condensate refrigerant.

Additionally, an additional sensible heat rejection, due the subcoolingof condensate, can also have an important contribution in the total heatrejection process inside of desuperheating if the wall temperature ofthe pipe is below of the saturation temperature of refrigerant.

Inside of the external desuperheater, the temperature difference betweenthe secondary coolant media (condensed water coming from evaporator),and the bulk temperature of the refrigerant can be several tens ofdegrees. This temperature difference is much higher than the oneobserved in the typical desuperheating process inside of standard airsource condensers (air-to-refrigerant bulk temp), which in turn can bejust some few degrees.

The fact that the condensation process can start before the refrigerantenters to the condenser is of importance for the efficiency increase ofair source condensers, since more area of the condenser will besubsequently intended to continue the saturated condensation process,which has higher heat transfer coefficients than the single-phasedesuperheating process between the hot gas and air.

To allow the heat transfer process, a desuperheater is located in anopen cavity condensation water pool where the cold water from theevaporator can drop and be in contact with the surface of thedesuperheater, allowing the condensation of the gas, and the evaporationof part of the water.

An exemplary embodiment of an air-conditioner, in particular a portableair-conditioner with such an external desuperheater is shown in FIG. 3.In FIG. 3, 301 is a compressor, 302 is an air source condenser, 303 isan external desuperheater, 304 is a condensation water pool where thedesuperheater is located and where the heat transfer process takesplace, 305 is a condensed water pipe from evaporator at low temperature,306 is a condenser fan.

The desuperheater heat exchanger 303 can in one embodiment be placed inan open pool 304, where the condensed water that drops from theevaporator is released by a pipe 305. In the pool, the heat exchangeprocess takes place due to the large temperature difference between bothfluids. Eventually, part of the condensed water is evaporated while thehot gas starts to condensate.

The desuperheater section is located in the bottom side after thecondenser 302, which allows the proper dragging of the evaporatedmoisture by the air stream coming from condenser. At these conditions,the air stream flowing through the condenser has higher temperature andlower relative humidity, therefore its capacity to retain the evaporatedwater that is generated in the desuperheater is also higher.

The design of the desuperheater comprises a pipe heat exchanger with oneor more passes, mounted inside of an open water pool. Further it ispossible to adjust the shape of the desuperheater heat exchanger 303 candiffer according the geometry and space of the air condition unit inwhich the desuperheater 303 is located.

Other possible variants can include different geometries of thedesuperheater 303, like the use of different types of fins or internalgeometries inside of pipes (micro finned internal surfaces), in order toincrease the heat transfer area of the desuperheater 303.

Additionally, the water pool can also adopt different configurations,depending of the particular geometry of the unit and the relativeposition of other components into the system. In that sense, thedesuperheater can have rectangular, cylindrical of any other design. Twopossible options are presented in the FIGS. 4 and 5.

Under certain humidity conditions, the desuperheater may not be able toremove all the condensate generated by the evaporator. In order toprevent a limited performance of the moisture evaporative system at highhumidity conditions, the system can be modified to include a water tankin the bottom of the condenser.

In FIG. 4, 401 represents a compressor, 402 is an air source condenser,403 is a desuperheater, 404 is a condensation water pool, 405 is acondensed water pipe from evaporator, 406 is the discharge line fromcompressor, 407 is the noise insulation coat that wraps the compressor.

FIG. 5 shows also a possible variation in which can be included thepossibility of using an auxiliary water tank which can store thenon-evaporated water in case of extreme humidity conditions.

In FIG. 5, 501 is the compressor, 502 is a cylindrical type condenser,503 is the desuperheater, 504 is the condensation water pool, 505 is thecondensed water pipe from evaporator, 506 is the discharge line fromcompressor, 507 is the noise insulation coat that wraps the compressor,508 is a noise insulation material around the compressor, 509 is anauxiliary water tank to recover the non-evaporated water, 510 is thebase for the condenser fan, 511 is part of the structure that holds allcomponents of the system.

In accordance with some embodiments a coating element can be wrappedaround the pipes that connect the desuperheater to the compressor andthe desuperheater to the condenser.

The apparatus as described herein can be configured to allow condensedwater dripping from the evaporator to be released over the pipes coveredby the coating element allowing the increase of the heat transfer areaof the desuperheater, and facilitating the evaporation and removal ofthe condensed water through the hot air steam that flows from condenser.

FIG. 6 shows a possible configuration of such an embodiment with acoating material over connection pipes.

In FIG. 6, 601 represents the compressor, 602 represents the air sourcecondenser, 603 represents the desuperheater, 604 represents the waterpool, 605 represents the condensed water pipe from evaporator, 606represents the condenser fan, 607 represents the coating materialcovering the discharge pipe and the connection between the desuperheaterand condenser.

In FIG. 6, the air stream after condenser has at low relative humidityand high temperature which allows the proper dragging of the evaporatedmoisture by the air stream coming from condenser.

The material of the coating element can be any natural or syntheticfabric manufactured with a cylindrical shape or with a flat mesh wrappedaround the pipes, allowing the temporary retention of the water aroundthe pipes while the evaporation of the water takes place.

Alternatively to the coating element, the pipes can be coiled by a helixshaped fin that can allow the dripping of the cold water from evaporatorand its evaporation by the heat exchange with the hot surface of thefinned tube.

FIG. 7 shows a possible embodiment of the coating element over theconnection pipes.

In accordance with another embodiment a water pump system can be addedto spray the non-condensed water from the auxiliary tank to the top ofthe condenser, where the pumped water is allowed to drip over thecondenser surface. In such an embodiment, the non-evaporated water cancontinue cooling down the temperature of the condenser surface, once therefrigerant is on saturated conditions, and simultaneously the systemcan pump water through the air stream that crosses the condenser. FIG. 8shows an embodiment including an auxiliary water pumping system toremove the non-condensed water.

The spray of the water has to be done preferable over the inner row ofthe condenser, to avoid that the water droplets that fill the gapsbetween fins can block the air path, creating additional pressure dropsin the air stream, and decreasing the condenser air flow rate.

In FIG. 8, 801 represents the compressor, 802 is the condenser, 803 isthe desuperheater, 804 is the condensation water pool, 805 is thecondensed water pipe from evaporator, 806 is the auxiliary water tank,807 is the water pump, 808 is the water pipe from the tank to the spraysystem, 809 is the water spray element in condenser top, 810 is thewater drainage system.

In accordance with other embodiments it is possible to take advantage ofthe low temperature of the condensed water coming from evaporator todecrease the condensing pressure of the cycle in other ways. For examplethe effect can be achieved alternatively by the release first thecondensed water over the condenser. Then, the remaining non-evaporatedwater can be collected in a water tank located for example at the bottomside after the condenser, and pumped over the desuperheater water pool.FIG. 9 shows an exemplary design of such an embodiment.

In FIG. 9, 901 is the compressor, 902 is the condenser, 903 is thedesuperheater, 904 is the non-evaporated water pool, 905 is thecondensed water pipe from evaporator, 906 is the auxiliary water tank,907 is the water pump, 908 is a water pipe from the tank to thedesuperheating water pool, 909 is a condenser water spray element placedin condenser top, 910 is the non-evaporated water drainage.

A difference between the embodiment from FIG. 8 and the one shown inFIG. 9 is the temperature difference between the heat sources and heatsinks of the different heat rejection sub processes. Constructively theversion proposed in FIG. 9 can have some advantages; however from theenergy efficiency standpoint the embodiment shown in FIG. 8 typicallyrepresents a more energy efficient solution.

One limitation in the embodiment shown in FIG. 9 is that the heattransfer area in de desuperheater typically has to be slightly largerthan the one proposed in the solution of FIG. 8 in order to allow thatthe bulk temperature of the refrigerant be closer to the thermodynamicequilibrium before the refrigerant enters into the condenser, since thetemperature difference between both fluids is smaller.

Using the air-conditioner as described herein provides a practicalsolution to minimize the size of air cooled condenses, commonly used inportable AC systems, but also for other systems working with Air ascoolant media.

The possibility of minimising the condenser size is achieved byproviding a zoning of the different heat exchange sub-processes. Alsodesuperheating of the hot gas delivered by compressor is provided.

By carrying out a desuperheating process outside of the condenser, thearea and internal volume that typically are intended to this process canbe re-assigned to complete the phase change process (condensation) andsubcooling inside of the air cooled condensers.

As the 2phase change and subcooling processes have larger heat transfercoefficients, the total area required in the heat rejection process inthe condenser will be smaller for a given capacity.

In turn, for a given size of condenser, the desuperheater can favour alarger enthalpy difference in the cycle, providing higher coolingcapacities in a standard system, without affecting significantly thepower consumption of compressor, and therefore, increasing also thecycle efficiency of the refrigeration cycle.

On the other hand, the design of the desuperheater allows the effectiveremoval of the undesired condensed water generated in the coolingprocess; at the same time that the Air conditioner takes advantage ofthe higher heat transfers coefficients obtained by the evaporation ofthe water.

An advantage of the technology described herein is that the heatrejection process in a portable AC unit can start before the refrigerantenters into the condenser, allowing either the minimization of astandard air cooled condenser size or the increase of cooling capacityfor a given condenser size.

Using the methods and devices as described herein makes it possible totake advantage of the larger temperature difference between both flowsallowing a compact and efficient design of the desuperheater, whichallows in turn a more effective condensing process. This effect isachieved by the increase of the heat transfer area destined to performthe 2-phase process of condensation, which provide better heat transfercoefficients and which is normally intended to the single-phase processof desuperheating in a conventional method.

The technology described herein can further improve the conventionalmethod used to remove the undesired condensed water generated in thenormal cooling process of an AC system, particularly in portable units.

In accordance with some embodiments a mechanism that splash condensedwater between the condenser rows. Through this method, thenon-evaporated water is pulverized in small droplets and atomised overthe condenser surface, forcing its removal through the air flow streamthat crosses the condenser, more than its evaporation.

A drawback of splashing the water could be that the water droplets thatmove into the air stream can eventually be agglomerated or condensateagain over the air exhausts ducts, dripping inside of the ducting systemand creating water leak problems for the user.

In addition, to the improvements on the thermodynamic cycle obtained bythe use to the technology described herein, there is an additionalbenefit offered by the reduction of the pressure drop inside of therefrigerant circuits of the condenser, especially for those geometrieswith small hydraulic diameters like mini tubes or micro-channels. Lowerpressure drops leads to lower power consumptions and more efficientsystems.

Another advantage of the technology described herein is the possibilityto increase the charge of refrigerant, without affecting the condensingpressure, to increase the refrigerant enthalpy difference in thecondenser but also in the evaporator, which eventually will allow toincrease the cooling capacity of the system.

By starting the condensation process in an external desuperheater it isalso possible to decrease the heat loses from compressor surface,increasing its reliability without affecting its mechanical performance.

The designs proposed for the desuperheater have the additional advantagethat prevents/reduce the resonances introduced by the tangentialvibrations due the varying torque produced by the compressor motor.

Hence, in accordance with the above an alternative to conventionalmethods that helps to decrease the condensing temperature of the cyclein a more efficient way is provided. This is achieved by an efficientzoning of the heat rejection processes using the condensed water thatdrips from the evaporator.

Hence a more efficient energy exchange process carried out by anexternal desuperheater installed between compressor and condenser. Thismethod takes advantage of the larger temperature difference between thehot discharge gas delivered by the compressor, and the condensed chillywater dripping from the evaporator surface.

1. An air-conditioner comprising: a compressor; a condenser; a flow pathextending from the compressor to the condenser; and a desuperheater inthe flow path.
 2. The air-conditioner according to claim 1, wherein theair-conditioner is a portable air-conditioner.
 3. The air-conditioneraccording to claim 1, wherein the desuperheater is located in an opencavity.
 4. The air-conditioner according to claim 3, wherein theair-conditioner is configured to direct condensation water to the opencavity.
 5. The air-conditioner according to claim 4, further comprisinga pipe configured to direct condensed water that drops from anevaporator to the open cavity.